1. Ultrasound Obstet Gynecol 2010; 36: 553–555
Published online 2 September 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.7711
Isolated single umbilical artery: need for specialist fetal
echocardiography?
D. DEFIGUEIREDO, T. DAGKLIS, V. ZIDERE, L. ALLAN and K. H. NICOLAIDES
Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital Medical School, London, UK
KEYWORDS: cardiac defect; fetal echocardiography; prenatal diagnosis; single umbilical artery; ultrasound
ABSTRACT
Objective To examine the association between single
umbilical artery (SUA) and cardiac defects and to
determine whether patients with SUA require specialist
fetal echocardiography.
Methods Incidence and type of cardiac defects were
determined in fetuses with SUA detected at routine
second-trimester ultrasound examination.
Results A routine second-trimester scan was performed
in 46 272 singleton pregnancies at a median gestation of
22 (range, 18–25) weeks and an SUA was diagnosed in
246 (0.5%). Cardiac defects were diagnosed in 16 (6.5%)
of these cases, including 10 (4.3%) in a subgroup of
233 with no other defects and in six (46.2%) of the 13
with multiple defects. In 11 (68.8%) of the 16 cases with
cardiac defects the condition was readily diagnosable by
evaluating the standard four-chamber view and the views
of the great arteries. In the remaining cases there was left
persistent superior vena cava or small ventricular septal
defect, where prenatal diagnosis may not be important
because they are not associated with adverse outcome.
Conclusion Although SUA is associated with an
increased incidence of cardiac defects it may not be
necessary to refer such patients for specialist fetal echocar-
diography because the defects are detectable by evaluating
standard cardiac views that should be part of the rou-
tine second-trimester scan. Copyright  2010 ISUOG.
Published by John Wiley & Sons, Ltd.
INTRODUCTION
A single umbilical artery (SUA) is found in about 0.5% of
pregnancies and is associated with chromosomal defects
and malformations of all major organ systems1,2. In
previous studies on a combined total of 1038 cases of SUA
diagnosed prenatally the prevalence of fetal abnormalities
was 33.6% (Table 1)3–15
. Consequently, the prenatal
diagnosis of SUA should motivate the sonographer to
undertake a systematic and detailed examination of the
fetal anatomy for the diagnosis or exclusion of associated
defects. In the reported series of SUA, the prevalence of
cardiac defects was 11.4%, but it is not stated whether
these were isolated or whether they were associated with
other, more easily detectable, defects (Table 1)3–15
.
In this study we examined the association between
SUA and cardiac defects with the aim of determining
whether patients with SUA require specialist fetal
echocardiography.
METHODS
All pregnant women booked for antenatal care and
delivery in our hospital are offered two ultrasound scans,
one at 11–13 weeks’ gestation as part of screening for
chromosomal defects16,17
and another at 20–23 weeks
for detailed fetal examination according to a standard
protocol. All scans are carried out by sonographers
who had obtained The Fetal Medicine Foundation
certificate of competence in the 20–23-week scan
(www.fetalmedicine.com). The standard examination
includes the use of color-flow mapping in the fetal pelvis
to visualize the two umbilical arteries and the diagnosis
of SUA. In all cases of SUA, the fetal heart is examined
either by an experienced fetal medicine consultant or
by a fetal cardiologist. This includes, as a minimum,
examination of the four-chamber view, outflow tracts
and transverse arches. Demographic characteristics and
ultrasound findings are recorded in a fetal database at
the time of the examination. Data on pregnancy outcome
were obtained from the hospital records.
We searched the fetal database to identify all
patients with an SUA among those singleton pregnancies
undergoing a routine second-trimester scan between
January 2000 and December 2008.
Correspondence to: Prof. K. H. Nicolaides, Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital Medical School,
Denmark Hill, London SE5 8RX, UK (e-mail: fmf@fetalmedicine.com)
Accepted: 28 May 2010
Copyright  2010 ISUOG. Published by John Wiley & Sons, Ltd. ORIGINAL PAPER

2. 554 DeFigueiredo et al.
Table 1 Prenatal sonographic studies reporting on the incidence of cardiac and other abnormalities in fetuses with single umbilical artery
Reference
Gestational age at
scan (weeks)
Total
(n)
Fetal
abnormalities (n (%))
Cardiac
defects (n (%))
Abuhamad et al. (1995)3 25 (10–40) 77 20 (26.0) 9 (11.7)
Catanzarite et al. (1995)4 16–39 82 41 (50.0) 15 (18.3)
Blazer et al. (1997)5 15 (14–16) 46 6 (13.0) 1 (2.2)
Ulm et al. (1997)6 21 (16–41) 103 58 (56.3) 10 (9.7)
Chow et al. (1998)7 29 (16–41) 118 37 (31.4) 19 (16.1)
Geipel et al. (2000)8 21 (13–39) 102 43 (42.2) 15 (14.7)
Budorick et al. (2001)9 2nd trimester 57 26 (45.6) 5 (8.8)
Gossett et al. (2002)10 22.8 (17–28) 103 29 (28.2) 18 (17.5)
Gornall et al. (2003)11 19 (19–20) 107 20 (18.7) 7 (6.5)
Martinez-Payo et al. (2005)12 20 (≥ 13) 40 6 (15.0) 1 (2.5)
Volpe et al. (2005)13 20 (17–22) 40 16 (40.0) 9 (22.5)
Granese et al. (2007)14 16–23 61 22 (36.1) 3 (4.9)
Lubusky et al. (2007)15 16–22 102 25 (24.5) 6 (5.9)
Total 1038 349 (33.6) 118 (11.4)
RESULTS
During the study period a routine second-trimester scan
was performed in 46 272 singleton pregnancies at a
median gestational age of 22 (range, 18–25) weeks. SUA
was diagnosed in 246 (0.5%) and in this group the median
maternal age was 34 (range, 16–44) years. One of the 246
women had diabetes mellitus and another had a family
history of congenital heart defect (CHD). None of the
women was taking any medications associated with CHD,
such as antiepileptic drugs or lithium.
The 246 cases with SUA were divided into three groups.
In the first group there were 223 cases in which no cardiac
or extracardiac defects were identified prenatally, but in
two of the live births from this group a ventricular septal
defect was detected postnatally. In the second group there
were 10 cases with no extracardiac defects but with a
cardiac abnormality that was diagnosed prenatally. In the
third group there were 13 cases with extracardiac defects
(multiple, n = 5; spina bifida, n = 2; ventriculomegaly,
n = 2; encephalocele, n = 1; hydrops, n = 1; unilateral
multicystic kidney, n = 1; pelvic kidney, n = 1) and in six
of these a cardiac abnormality was diagnosed prenatally.
In total, cardiac defects were diagnosed in 16 (6.5%)
cases, including 10 (4.3%) of 233 with no other defects
(Groups 1 and 2) and in six (46.2%) of the 13 with at
least one extracardiac defect (Table 2).
In the 223 cases of isolated SUA, there were 214
(96.0%) live births, three neonatal deaths (one due to birth
asphyxia and two due to prematurity) and six intrauter-
ine deaths (five due to fetal growth restriction and one
unexplained). In the group of 23 cases of SUA with pre-
natally detected fetal defects, there were 12 (52.2%) live
births, seven terminations of pregnancy at the request of
the parents and four intrauterine deaths.
In 185 (75.2%) of the 246 cases of SUA the patients had
first-trimester screening for chromosomal defects in addi-
tion to the second-trimester scan. The incidence of cardiac
or extracardiac defects in the second-trimester scan was
4.3% (8 of 185) in those with first-trimester screening and
24.6% (15 of 61) in those without (chi2
test P < 0.001).
Table 2 Cardiac defects in fetuses with single umbilical artery in
the presence and absence of other defects classified according to the
standard sonographic view necessary for prenatal diagnosis
Cardiac defect
No other
defects
(n = 233)
Other
defects
(n = 13)
Detectable in the four-chamber view
Atrioventricular septal defect 1 (0.4) —
Atrioventricular valve dysplasia — 1 (7.7)
Coarctation of the aorta 3 (1.3) 1 (7.7)
Detectable in the great artery view
Tetralogy of Fallot 1 (0.4) 2 (15.4)
Double outlet right ventricle
and pulmonary atresia
1 (0.4) —
Transposition of the great arteries 1 (0.4) —
Requires specialist echocardiography
Ventricular septal defect 2 (0.9) 2 (15.4)
Left superior vena cava 1 (0.4) —
Total 10 (4.3) 6 (46.2)
Data are given as n (%).
DISCUSSION
The findings of this study confirm the previously reported
association between SUA and cardiac defects3–15
. The
incidence of cardiac defects was much higher in the pres-
ence of extracardiac abnormalities than in cases without
other abnormalities (46.2% vs. 4.3%).
The overall incidence of cardiac defects in fetuses
with SUA inevitably depends on the design of the
study and whether the patients included constitute a
routinely screened unselected population, as in our study,
or whether it includes patients referred to a specialist
center from a routine service following the diagnosis of
cardiac or other defects. Another important factor that
influences both the incidence of SUA and the coincidence
of cardiac as well as other defects in the second trimester is
the proportion of pregnancies undergoing first-trimester
screening. Early diagnosis of chromosomal and other
major defects often results in termination of pregnancy
and consequently a substantial reduction in the incidence
Copyright  2010 ISUOG. Published by John Wiley & Sons, Ltd. Ultrasound Obstet Gynecol 2010; 36: 553–555.

3. Single umbilical artery and CHD 555
of such abnormalities in the second trimester. A study
of pregnancies undergoing chorionic villus sampling at
11–14 weeks’ gestation reported that the incidence of
SUA was 5.9%, which is substantially higher than the
incidence of 0.5% in our patients, and that half of
the fetuses with SUA had chromosomal defects, mainly
trisomy 18, which is strongly associated with cardiac and
multiple other defects18. In our study the incidence of fetal
defects in the second-trimester scan was approximately
six times higher in those who had not had first-trimester
screening than in those who had (24.6% vs. 4.3%).
The pattern of cardiac defects was similar in the groups
with and without other abnormalities and was also sim-
ilar to that reported in previous studies of fetuses with
SUA3–15
. In two-thirds of the cases the cardiac defect
was readily diagnosable by evaluating the standard views
of the four chambers and great arteries. In the case of
left persistent superior vena cava and small ventricular
septal defect diagnosis of the defect would require a more
detailed scan. However, prenatal diagnosis of such defects
may not be important because they are not associated with
adverse outcome.
In all cases with SUA the fetal heart was examined either
by an experienced fetal medicine consultant or by a fetal
cardiologist. However, a limitation of the study, which
may have resulted in underestimation of the incidence of
cardiac defects, is that the neonates had routine clinical,
rather than detailed cardiological, examination.
The main issue raised by our findings is whether patients
with SUA detected at the routine second-trimester scan
should be referred for specialist fetal echocardiography.
Certainly the incidence of cardiac defects in such patients
(4.3%) is substantially higher than in patients with a
family history of cardiac defects and diabetes mellitus
(about 2%), which are widely accepted as indications for
fetal echocardiography. The alternative argument is that
examination of the fetal heart should be an integral part of
the routine second-trimester scan and that sonographers
undertaking such an examination should be competent in
obtaining and evaluating the four-chamber view and out-
flow tracts19
. Consequently, detection of an SUA should
alert the ultrasonographer to examine more carefully the
standard cardiac views and refer for specialist echocar-
diography only those with a suspected abnormality. If the
routine scan does not include appropriate examination
of the heart, patients with SUA should be referred to a
specialist in fetal echocardiography.
ACKNOWLEDGMENT
This study was supported by a grant from The Fetal
Medicine Foundation (Charity No: 1037116) and is part
of the PhD thesis of D. DeFigueiredo, Universidade de
Brasilia, Brasilia, Brazil.
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Copyright  2010 ISUOG. Published by John Wiley & Sons, Ltd. Ultrasound Obstet Gynecol 2010; 36: 553–555.